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1950 INFRARED WITH ELECTRIC-FLASH 489
A commercial 10,000-w-sec flash unit having a guide number for Kodachrome of 250 could be used to photograph in infrared an area of several thousand square feet at an aperture of //3.5. A press photographer's portable strobe unit could be used for figure length photographs at perhaps //2.5, and finally, working toward smaller and smaller areas, infrared photomicrographs with electric-flash should be well within the realm of possibility. Figure 4 is an infrared photograph taken with a flash unit using a guide number nearly 50% higher than the guide number which normally would be used for Kodachrome.
A DATA RECORDER USING ELECTRIC-FLASH INFRARED LIGHT Development
An ideal application of electric-flash as a source of infrared light is represented in a small automatic data recorder or "cockpit observer" for photographically recording instrument readings in aircraft during flight tests. The development of an instrument for use on extended flights was sponsored by the Civil Aeronautics Administration and participated in by the Fairchild Camera Co. through a contract with the CAA in 1936. It was extended through a contract with Eastman Kodak in 1941. The intention was to filter out all visible light and photograph with infrared in order to remove all possibilities of distracting the pilots. Incandescent sources were originally used, but the relatively long exposures required resulted in blurred images due to aircraft vibration. Electric-flash as the infrared light source offered the possibility of eliminating this defect.
A CAA Contract with Edgerton, Germeshausen & Grier, Inc., in 1943 resulted in two special 16-mm cameras and an experimental 110-v a-c electric-flash unit. The cameras constructed by the Eastman Kodak Co. were adaptions of the standard 16-mm Magazine Cine Kodak. The spring motors were removed and electric motordrives substituted. Fast-acting overriding shutters were incorporated to give a short exposure despite the slow operating speed of two frames per second. This was necessary to minimize the effect of daylight which would have superimposed an additional exposure of long duration. Contact synchronizers with zero time delay were also incorporated for synchronizing the electric-flash. The cameras proved to be very satisfactory for this application.
In 1947 the application requirements of the equipment were changed to those of a flight test recorder, in particular, for small aircraft. Inasmuch as the principal requirement was to have a source of